Environmentally persistent free radicals (EPFRs) have been found at levels 30 times higher in the pentachlorophenol (PCP) contaminated soils from a Superfund site - a former wood-treatment facility, than in pristine soil samples from the neighboring area. This finding is important due to the widespread use of PCP, potential of toxicity of EPFRs, potential exposure to these EFPRs due to wind blown dust from the site, their migration to and through ground waters as well as dermal exposure. Thus, a fundamental understanding of how the EPFRs can be formed in soils that have been contaminated with PCP is needed. Due to the complexity of soils, a number of pathways could account for the formation of EPFRs. This project will systematically explore the formation of EPFRs within PCP-contaminated soils through three Specific Aims: 1) Physically separate, chemically edit and characterize the organic and inorganic components of both contaminated and non-contaminated soils; 2) Determine the main soil component(s) responsible for the formation of EPFRs in the contaminated soil; and 3) Utilize model systems based on the findings from Specific Aim-1 to gain insight into the natural 'in-situ' formation of radicals in the contaminated soil. This project is unique as it addresses real world samples. This means that this project will act as a testing ground for the universality of some of the concepts derived for thermal EPFR formation pathways in Project 1, and in doing so, will act as a feedback loop to Project 1. This feedback loop will be further strengthened by collaborations with Project 6. Select samples from Aim-1, Aim-2, and Aim-3 will be provided to the biomedical Projects 2, 4 and 5 through the collaboration with the Materials Core. In addition to the samples, this project will provide the basic chemistry to understand any observed cardiac and pulmonary dysfunction induced by inhalation of these EPFR-containing samples.